Improvement in galvanizing metal



m STATES PATENT OFFICE.

WILLIAM H. WAHL AND EDWARD Y. ELTONHEAD, OF PHILADELPHIA, PENNSYLVANIA,ASSIGNORS OF ONE-THIRD OF THEIR RIGHT TO CALEB H. HORNE, OF SAME PLACE.

|MPROVEMENT IN GALVANIZING METAL.

Specification forming part of Letters Patent No. 221,200, dated November4, 1879; application filed To all whom it may concern:

Be it known that we, WILLIAM H. WAHL and EDWARD Y. ELTONHEAD, both ofPhiladelphia, Pennsylvania, have invented a new and useful Improvementin Galvanizing, of which the following is a specification.

Our invention consists in scaling and clearing iron objects prior tocoating the same with zinc or other metals by subjecting the objects toan acidulated aqueous solution of chloride of zinc, as describedhereinafter.

In preparing the bath we dissolve chloride of zinc in water and add fromfive to ten per cent. of mnriatic acid, the solution being afterwardconcentrated by evaporation until it has become of a sirupy consistency.This concentration is not absolutely essential; but we have found theacidulated chloride to be more active in the performance of its duties,when deprived of a portion of its water, and the action is facilitatedby the application of heat.

We may remark here that a cheap way of making this solution is toutilize the precipitated zinc iron alloy of galvanizing baths, which iscommonly called dross, by converting it into a chloride of zine, andthen dissolving this cheap chloride in water and adding the properamount of acid. The iron objects are immersed 'in this solution, and arepermitted to remain therein until entirely freed from the scale oroxide. This may require from fifteen minutes to two hours, according tothe thickness and tenacity of the scale on the surface of the iron.

While the chloride of zinc alone or the acid alonepossesses the propertyof clearing scale from the surface of iron, wehave found that whencombined each ingredient enhances the activity ofthe other, andconsequently that the clearing effect is more rapidly accomplished bythe acidulated bath than by the chloride

